1. Technical Field
The present invention relates to a method for emitting a jet of air in a liquid ejecting apparatus, and the apparatus. More particularly, the invention relates to an air jet emission technique that is useful when applied to a large format printer.
2. Related Art
A liquid ejecting apparatus is provided with a liquid ejecting head and performs predetermined printing by emitting liquid droplets from the liquid ejecting head onto a medium such as paper, cloth, a film, or the like. A typical example of such a liquid ejecting apparatus is an ink-jet recording apparatus (hereinafter may be simply referred to as “recording apparatus”), which is provided with an ink-jet recording head (hereinafter may be simply referred to as “recording head”) for ejecting ink droplets. A so-called large format printer, which is a kind of such a recording apparatus, performs printing on large-sized paper. The body of such a large format printer is mounted on its stand. In such a large format printer, a medium is transported along a guide and is fed into the printer body while being guided by the guide through an opening formed at an upstream side, which is the entrance side of the printer body, and, after completion of predetermined printing by a recording head inside the printer body, is outputted through an opening formed at a downstream side, which is the exit side of the printer body. The medium is in the form of a roll and is rotatably supported by the stand. The medium is unreeled and is fed into the printer body from the upstream side. As mentioned above, the recording head performs predetermined printing, and, after that, the medium is outputted from the exit side of the printer body.
In such a large format printer, the transportation path of the medium supported in the form of a roll by the stand and transported along the guide before being fed into the printer body at the upstream side as viewed from the recording head is long. Because of the long transportation path, the probability of settlement of dust (fiber particles, etc.) drifting in the air onto the surface of the unreeled medium is high. If printing is performed on such a medium the surface of which is contaminated with dust, it causes displacement in the landing positions of ink droplets ejected, resulting in poor print quality.
A known technique for preventing the nozzles of the recording head of an ink-jet recording apparatus from being clogged with paper dust or other dust and thereby guaranteeing great reliability is disclosed in JP-A-2003-220695. In the structure disclosed in JP-A-2003-220695, an air stream is produced inside the body of the apparatus at an upstream side as viewed from the recording head so as to prevent dust, etc. from entering the body of the apparatus. In this structure, a voltage is applied between a transportation unit and the recording head to apply electric charges to dust, etc. drifting in the air, thereby causing the dust, etc. to be attracted onto a medium by static electricity.
However, in JP-A-2003-220695, there is a possibility that the air stream produced at the upstream side as viewed from the recording head will cause displacement in the landing positions of ink droplets ejected. Moreover, when the charged dust is attracted onto the medium, depending on the attitude of the dust such as fiber particles, etc., there is a risk of the re-settlement of the dust into the nozzles of the recording head and the resultant running of ink droplets down onto the medium via the fiber particles. In both of these cases, print quality will be poor.
The problems described above are not unique to an ink-jet recording apparatus. The same problems could also arise in various kinds of liquid ejecting apparatuses.